This invention pertains generally to ultrasonic imaging and, more particularly, to an apparatus and method for ultrasonic imaging of small cavities with catheter based devices.
In recent years, intravascular ultrasound (IVUS) imaging systems have been designed for use by interventional cardiologists in the diagnosis and treatment of cardiovascular and peripheral vascular disease. Such systems enhance the effectiveness of the diagnosis and treatment by providing important diagnostic information that is not available from conventional x-ray angiography. This information includes the location, amount and composition of arteriosclerotic plaque and enables physicians to identify lesion characteristics, select an optimum course of treatment, position therapeutic devices and promptly assess the results of treatment.
Such IVUS systems generally include an IVUS device having one or more miniaturized transducers mounted on the tip of a catheter or guide wire to provide electronic signals to an external imaging system. The external imaging system produces an image of the lumen of the artery or other cavity into which the catheter is inserted, the tissue of the vessel, and/or the tissue surrounding the vessel. Problems encountered with these systems include clearly visualizing the tissue around the catheter, and identifying the precise location of the image with regard to known spatial references, such as angiographical references.
Some of the ultrasonic imaging catheters currently in use are xe2x80x9cside viewingxe2x80x9d devices which produce B-mode images in a plane which is perpendicular to the longitudinal axis of the catheter and passes through the transducer. That plane can be referred to as the B-mode lateral plane and is illustrated in FIG. 1. There are also xe2x80x9cforward viewingxe2x80x9d devices that produce a C-mode image plane as illustrated in FIG. 2 which is perpendicular to the axis of the catheter and spaced in front of the transducer. Other forward viewing devices produce a B-mode image in a plane that extends in a forward direction from the transducer and parallel to the axis of the catheter. That plane is referred to as the B-mode forward plane and is illustrated in FIG. 3. The forward viewing devices are particularly advantageous in that they allow the physician to see what is in front of the catheter, and they also allow imaging in areas which cannot be crossed with the catheter.
One problem with imaging catheters heretofore provided is that a given type of IVUS catheter can provide high quality images in only one of the mode planes. There are no known devices, for example, which can provide both B-mode forward imaging and C-mode imaging. As such there exists in the art a need for an ultrasonic imaging transducer and method of the above character which can overcome the limitations and disadvantages of the prior art as well as be able to provide images in multiple planes.